Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 14
JavaScript Programming with
ASP.NET AJAX
ASP.NET AJAX offers many extensions to JavaScript, providing object-oriented features
such as namespaces, inheritance, interfaces, enumerations, and more. These functionalities
assist you in developing applications by providing more robust and structured
language features, making it easier to maintain and add new features to your applications.
In this chapter, you’ll look at these extensions to JavaScript, starting with the objectoriented
extensions, and then moving into some of the data type extensions, including
arrays, Booleans, and dates.
Object-Oriented Extensions to JavaScript
JavaScript, as its name suggests, is a scripting language, and thus hasn’t been designed
for higher-order functionality. As Ajax gains traction, requirements for applications are
becoming more and more sophisticated, and the language in which they are being built
needs to evolve in response.
Thus, ASP.NET AJAX has brought about object-oriented extensions to JavaScript to
make the programmer’s life a little easier. Please note that these aren’t changes to the
JavaScript interpreter—they are libraries built into JavaScript itself—so no changes to the
browser are needed to make them work. In this section, you’ll look through some of the
object-oriented features, including classes, namespaces, inheritance, interfaces, enumerations,
and reflection.
Using Classes in JavaScript
A class is how you define an object, where an object is an instance of a class. For example,
a car may be a class, but a specific car such as Bob’s 1995 Honda is an object that is
derived from that class, because his Honda is, in fact, a car.
You use a class to define what the properties, methods, and events of an object will
be. So, keeping the car example, a property is something that defines an attribute of the
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